A conventionally known piston for an internal combustion engine, which is disclosed, for instance, in Patent Document 1, is provided with a non-adiabatic region and an adiabatic region. The non-adiabatic region is positioned laterally relative to an intake flow and disposed on the upper surface of the piston. The adiabatic region is a region other than the non-adiabatic region. The presence of the adiabatic region makes it possible to reduce cooling loss.